Review of carbon nanotube-based flexible wearable strain sensors: From materials to applications for human body

Flexible wearable sensors provide practical advantages, including conformability to complex human-body surfaces and maintaining stable, accurate sensing during motion. These characteristics are enabled by sensor designs with diverse structural forms tailored to dynamic, on-body environments. Such applications require materials that offer both excellent manufacturability and reliable sensing performance. Carbon nanotube (CNT)-based polymer composites integrate the superior electrical conductivity of CNT with the mechanical flexibility and manufacturability of polymers, making them well-suited for fabricating flexible wearable strain sensors. This review systematically summarizes recent advances in flexible strain sensors based on various CNT/polymer composites, with emphasis on material form and microstructure–performance relationships. It highlights the role of microstructural engineering in tailoring sensor performance to elucidate in depth the influence of composite architecture on sensing behavior. Development pathways from raw materials to device fabrication are detailed, followed by discussions on practical applications in health monitoring, motion detection, and human–machine interaction. Finally, key challenges and prospects are outlined for future research. This review offers a unique material-centered framework that integrates composite design, microstructure control, and multifunctional application to guide the optimization of flexible CNT-based strain sensors for wearable devices.